1. Field of the Invention
This invention relates to the use of certain substituted organic peroxides containing a polar group as initiators in anaerobic curing adhesive and/or sealant compositions.
2. Prior Art
Adhesive and sealant compositions based on acrylate, e.g., methacrylate, monomers polymerizable by free-radical initiation are known in the art. Likewise, anaerobic compositions are known in the art (see, for example, U.S. Pat. Nos. 2,895,950, 3,043,820, and 3,218,305). Anaerobic compositions are characterized by their ability to remain liquid in the presence of air, but cure to a strong adhesive bond when air is excluded, as by assembling a mated nut and bolt to which the composition has been applied.
While anaerobic monomers were initially limited to alkylene glycol diacrylates, more recently urethane-acrylate monomers, such as are disclosed by Gorman et al. in U.S. Pat. No. 3,425,988, have been developed. These materials may be regarded as the reaction product of a polyisocyanate (e.g., toluene diisocyanate) with a mono-acrylate having a reactive hydrogen atom in the alcoholic portion thereof (e.g., hydroxypropyl methacrylate).
Various other urethane-acrylate-type monomers have been developed more recently by Baccei. One of these monomers, described in copending application Ser. No. 546,250, filed Feb. 3, 1975, comprises a urethane-acrylate-capped polybutadiene polyol or polyamine. Another related monomer, described in copending application Ser. No. 557,740, filed Mar. 12, 1975, and now abandoned, comprises a urethane-acrylate-capped poly(methylene)ether polyol. Still another related monomer, described in copending application Ser. No. 557,564, also filed Mar. 12, 1975, comprises a urethane-acrylate-capped vinyl grafted poly(alkylene) ether polyol.
Still other anaerobic monomers utilizing hydroperoxide cure initiators are disclosed in U.S. Pat. Nos. 3,720,656, 3,631,154 and 3,651,036.
Methods of using anaerobic system are disclosed in the references mentioned above, as well as in U.S. Pat. Nos. 3,547,851, 3,625,875 and 3,672,942, copending application serial number 356,679, filed May 2, 1973, and now abandoned and copending application Ser. No. 620,905, filed Oct. 8, 1975, among others. Among the many known uses for anaerobic compositions are thread-locking, impregnation, gasketing, structural adhesives, and manufacture of tapes.
The disclosures of all the above patents and applications are incorporated herein by reference.
The compositions disclosed in all the preceding patents and applications share the characteristic that hydroperoxides are typically relied upon to provide effective initiation while not significantly degrading the stability, i.e., shelf life, of the composition.
Clearly, a compound offering a viable alternative to hydroperoxides would be a very useful and valuable addition to anaerobic adhesive technology.